Imaging the X-37B robotic spaceplane mission OTV 7

OTV 7 imaged from Leiden at 12 Feb 2024. Click image to enlarge

In my previous post, I wrote about the first on-orbit detections, by Tomi Simola, of the US Space Force's X-37B space plane mission OTV 7, and how it is in an orbit that is certainly unusual for a space plane.

Yesterday (February 12, 2024) I finally had a clear sky, and an almost near-zenith pass of OTV 7 in the early evening just after twilight. So I could finally image it too. 

Using the ZWO ASI 6200MM PRO with a 1.2/85 mm lens, OTV 7 showed up well in the imagery, as a reasonably bright object that was not difficult to detect. Above is one of the images, a 10 second exposure near 19:06 UTC while OTV 7 was over Europe at ~6700 km altitude, descending towards perigee.

The orbit is now a bit better constrained, and about  38600 x 300 km at 59.15 degree inclination. Perigee is currently over the equatorial region. The image below shows the orbit, and the orbital position of OTV 7 around the time I imaged it:

click image to enlarge

OTV 7 was several minutes early on one day old elements, meaning it appears to be actively manoeuvering. This fits an X-37B, the previous OTV missions (all to LEO) were also frequently manoeuvering. 

It is possible that the spacecraft is using a continuous thrust ion engine.

In the current Highly Elliptical Orbit (HEO), the orbital velocity at perigee is close to 10.2 km/s, which is 2.4 km/s more than in a Low Earth Orbit (previous X-37B missions all went to Low Earth Orbit). To eventually land the spaceplane, the orbit likely will be circularized first, by lowering apogee drastically, perhaps with the help of aerobraking in perigee, before doing a deorbit and landing.

This is my current orbital fit, which is still up for improvement, based on observations by Tomi Simola, Eelke Visser, Scott Tilley and me:

OTV 7
1 58666U 23210A   24044.12782730 0.00000000  00000-0  00000+0 0    05
2 58666  59.1696   4.0545 7416334 167.8228 233.0020  2.09261279    07